1. Field of the Invention
The present invention relates to power drive systems, and more particularly to a power drive system for a sliding door which in response to manual movement by a user operates an electric motor to overcome forces created during the manual movement of the sliding door.
2. Description of Related Art
In various types of automotive vehicles, including minivans, delivery vans, and the like, it has become common practice to provide a vehicle body with relatively large side openings that are located immediately behind front doors and which are opened and closed with a sliding side door. The sliding side door is typically mounted with upper and lower hinge members to horizontal tracks on the vehicle body for guided sliding movement between a close position flush with the vehicle body, closing the side opening, and an open position located outward of and alongside the vehicle body rearward of the side opening. The sliding side door may be operated manually or with a power drive system to which the present invention is directed.
Examples of conventional power drive systems for automatically opening and closing the sliding side door are described in U.S. Pat. Nos. 6,481,783; 6,464,287; 6,435,600; 6,256,930; 6,079,767; 5,833,301; 5,644,869; 5,536,061; 5,434,487; 5,203,112; 5,168,666; and 4,612,729. Various power drive systems utilize a cable, chain, or belt to open and close the sliding side door. For example, U.S. Pat. No. 5,168,666 discloses a door drive device which includes a guide rail in a vehicle body defining a path along which a side door moves. An endless belt extends around first and second pulleys which are arranged at spaced positions within the vehicle body. A bracket is provided for connecting a portion of the endless belt to the side door and a reversible electric motor drives the first pulley thereby moving the side door between an open position and a close position.
Commonly assigned U.S. Pat. No. 7,032,349, which is hereby incorporated by reference as if fully set forth herein, discloses a door drive system including a frame fixedly secured to a motor vehicle. A motor is fixedly secured to the frame and adapted to convert power into a rotational output force. The motor includes a non-ferrous core. A set of pulleys and rollers are fixedly secured to the frame at predetermined positions to direct the path of a continuous belt. The belt is fixedly secured to a sliding door such that the motor moves the belt and the sliding door bi-directionally between an open position and a close position. Sensors are used to determine the position of the sliding door, the speed thereof and whether the sliding door is being moved manually. The sensors may be used to detect the presence of a back-driving force in an interfacing transmission between the motor and the belt. Once sensed, the information is transmitted to an electronic controller allowing it to operate the motor. In this manner, the motor would be operated to keep up with the movement of the sliding door eliminating the need for the operator to manually overcome the losses due to the motor and the interfacing transmission.
It remains desirable, however, to provide a power drive system including a simple and robust differential belt tensioner operatively coupled between the belt and the sliding door. It is also desirable to provide sensors for sensing movement of the belt during manual movement of the sliding door and sending a signal based on sensing this belt movement to operate a motor to overcome forces resulting from the manual movement of the sliding door. It is further desirable to operate the motor to provide force assist to further reduce efforts during the manual movement of the sliding door.